Although bandwidth is set differently between uplink and downlink, only one carrier is generally considered in the conventional wireless communication system. The carrier is defined by a center frequency and a bandwidth. A multiple carrier system uses a plurality of component carriers (CCs) having narrow bandwidth than full bandwidth.
A multiple carrier system can support backward compatibility for legacy systems and also increase data rate significantly through multiple carriers.
Long term evolution (LTE) based on 3rd Generation Partnership Project (3GPP) Technical Specification (TS) Release 8 is a promising, next-generation mobile communication standard. A 3GPP LTE system is a single carrier system supporting only one bandwidth (i.e., one CC) among 1.4, 3, 5, 10, and 20 MHz. However, LTE-Advanced (LTE-A), which is an evolved version of the 3GPP LTE, employs multiple carriers.
In a single carrier system, control channels and data channels are designed based on a single carrier. However, it can be inefficient if a multiple carrier system employs the channel structure of a single carrier system as it is.